A polymer electrolyte membrane fuel cell (PEMFC) for a vehicle may have reduced performance due to deterioration of an electrode (Pt/C, platinum supported in a carbon support) configuring a membrane electrolyte assembly (MEA) and a membrane after it is operated for a predetermined time. In particular, an oxide film (Pt-oxide) formed on a platinum surface of a cathode having several nano particle size has been known as having an effect of hindering reaction O from being adsorbed onto the platinum surface to reduce an oxygen reduction reaction (ORR) rate of the cathode. CO of several ppm included in fuel is chemically adsorbed into platinum of an anode, which leads to reduced hydrogen oxidation reaction (HOR) efficiency. Further, a local increase in temperature occurring during a high power and low humidity operation shrinks a pore structure of the membrane or rearranges an SO− terminal group to cause a reduction in ion conductivity. It has been reported that the SO− terminal group of a binder causes specific adsorption of an anion into a surface of a platinum catalyst under the low humidity operation conditions to reduce catalyst activation. The SO in air poisons a cathode catalyst to reduce the catalyst activation. Since the reduction in performance of the fuel cell stack due to a change in an internal structure of an electrode membrane is due to a reversible deterioration, the performance of the fuel cell stack may be partially recovered. However, research or patents thereon are seldom reported.
The present applicant has tried various methods for improving the reduction in performance of the fuel cell stack due to the reversible deterioration as described above. As the methods, there are a “method for recovering performance of a fuel cell by a hydrogen storage method (Patent Laid-Open Publication No. 10-2014-0017364)” to supply H of high temperature (70° C.) to a cathode and seal and store both of an anode/cathode under hydrogen atmosphere for 12 hours, a “method for recovering performance of a fuel cell stack by air braking (Patent Application No. 10-2013-0146740)” to supply hydrogen to an anode (at the same time, with a stop of air supply) and then continuously applying a load of 5 to 10 A to induce hydrogen pumping to a cathode, a “method for recovering performance of a fuel cell stack by a reverse potential pulse (Patent Application No. 10-2013-0131495)” to substitute a pole and then apply a high output pulse load in a state in which air is supplied to an anode and hydrogen is supplied to a cathode. All the methods as described above induce the generation of hydrogen to the cathode side to accelerate a reduction in platinum oxide. However, all the methods do not yet effectively improve the deterioration due to impurities such as CO and SO− adsorbed into the platinum catalyst of the anode among the deterioration causes of performance of the fuel cell.